Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) are used extensively throughout the developed nations of the world. They are used in military, commercial, and consumer applications in a broad range of devices.
As is well known, GPS (and other GNSSs) includes multiple signals, some designed for public/civilian use and some designed only for authorized users (e.g., the US Department of Defense). For example, the complex signals include an I signal and a Q signal that is orthogonal to the I signal. At the L1 frequency of 1575.42 MHz, the I signal may include a P(Y) code for authorized users and the Q signal may include a course/acquisition (C/A) code, an L1C code, and an M code (the latter being for authorized users). At the L2 frequency of 1227.60 MHz, the I signal may include the P(Y) code for authorized users and the Q signal may include an L2C code and an M code (the latter being for authorized users).
The highest levels of positional accuracy can be obtained from the P(Y) and M codes. A slightly-less accurate position can be obtained by using more than one of the C/A, L1C, L2C, or certain aspects of the P(Y) codes (even without knowing the code used to create the P(Y) code). GPS receivers that receive multiple ones of these signals/codes can be complex and expensive and often include custom designs. Driven partially by consumer demand, simpler, inexpensive GPS receivers have been developed that provide a reduced, but often adequate, level of positional accuracy for consumer applications. These inexpensive receivers may only receive the L1 signal and may use only the C/A or L1C code.
It is against this background that the disclosed hardware front-end for a GNSS receiver has been developed.